JP2001002822A - Uniaxially or biaxially stretched polyester resin foamed sheet and film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide uniaxially or biaxially stretched polyester resin foamed sheets and films having a low apparent density and a sufficiently high crystallinity. SOLUTION: This polyester resin foamed sheet has a melt strength of higher than 1 cN at 280 deg.C, a melt viscosity of at least 1,500 Pa.s at 280 deg.C for a shear rate which tends to 0 and a crystallization rate such that heating at 120 deg.C for 10 min gives crystallinity of 30-35%. Desirably, the bulk density is in the range of 100-1,000 kg/m3 and the thickness is 0.03-1 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to uniaxially and biaxially stretched foam films and sheets made of polyester resin having high mechanical properties and useful optical properties.

[0002]

2. Description of the Related Art Polyester resin films have excellent mechanical, electrical and chemical resistance properties.
Widely used in various technical fields. In particular, a biaxially stretched film made of polyethylene terephthalate is superior to other films from the viewpoints of dimensional stability and tensile properties, particularly high elastic modulus.

[0003] The disadvantages, however, are mainly the very high relative density and the fact that in the information technology field, for example electronic whiteboards and similar devices, large amounts of white pigments have to be filled in order to be sufficiently opaque. Also have. Various methods are known for producing a foamed film or sheet made of a polyester resin. Thick low-density foamed material made of polyester resin has high heat insulation properties, which hinders effective cooling of the internal part of the material discharged from the extruder, and has a relatively high degree of crystallinity. And it is difficult to reduce it.

[0004] Density is 600~700kg / m ³ under a and capable or crystallization with a crystallinity, a method of uniaxially or biaxially stretching a foam sheet made of a polyester resin is not previously known. A problem with uniaxial and biaxial stretching of such low density foamed sheets is that the sheets may break during stretching. Further, poly (1,4-dimethylolcyclohexyl) terephthalate (poly (1,4
It is known from WO 97/33948 to produce labels from polyester foam films that can also be uniaxially or biaxially stretched when obtained from an amorphous resin such as -dimethylolcyclohexile) terephthalate) or amorphous copolyethylene terephthalate-isophthalate. I have. The ability to obtain uniaxially and biaxially oriented polyester resin foam sheets or films having a low apparent density and a sufficiently high degree of crystallinity would be of considerable advantage, especially in view of the improved mechanistic properties of such sheets and films.

[0005]

The problem of breakage and other problems
The bulk density is 700kg / m without disadvantage of
³Less than 400 kg / m³Less than
Crystallinity is 30 when heated at 120 ° C for 10 minutes.
Has a crystallization rate that can reach as high as ~ 35%
For aromatic polyester resin sheets and films
Uniaxial and biaxial stretching is possible,
Low apparent density, high mechanical properties, especially high modulus
And high impact resistance and high reflectivity associated with spark reflectivity
Stretched sheet or film with high translucency or opacity
It was discovered that the film could be obtained. Preferably, 12
Crystallinity obtained by heating at 0 ° C. for 10 minutes is 5 to 3
5%. The height of the produced stretched sheet or film
Shock resistance is surprisingly high for sheets and films before stretching.
Considerably higher than. Here, the above thickness, crystallinity, etc.
And biaxial stretching of foamed sheets with density and density properties
Is that these seats are above a certain limit and
Polyester tree with high melt strength and melt viscosity value
It was found to be suitable when obtained from fat.

[0006]

That is, the present invention has a dissolution strength of more than 1 centinewton at 280 ° C., and at least 1500 Pa.s. uniaxially or biaxially stretched foamed sheet and film made from an aromatic polyester resin having a crystallinity that can reach a value of 30 to 35% when heated at 120 ° C. for 10 minutes. About. Further, the present invention relates to a uniaxially or biaxially stretched foamed sheet and a film characterized in that the bulk density value is in a range of 100 to 1000 kg / m ³ and the thickness is 0.03 to 1 mm. Further, the crystallization ratio of the resin is 120
The present invention relates to a sheet and a film having a crystallization ratio at which the degree of crystallization is 5 to 20% when heated at 10 ° C. for 10 minutes.

Further, the present invention relates to a sheet and a film characterized in that 0.5 to 10% by weight of a polyamide is mixed with a polyester resin, and the polyamide is preferably polym-xylylene adipamide. .
A sheet and a film, wherein the polyester resin is polyethylene terephthalate or copolyethylene terephthalate-isophthalate containing 2 to 15 mol% of an isophthalic acid unit.

[0008] The present invention further relates to a multilayer material comprising uniaxially and biaxially stretched foamed sheets or films and one or more layers of other materials adhered to one or both sides of the foamed sheets or films. A multilayer material characterized in that at least one layer adhered to the foamed sheet or film is copolyethylene terephthalate-isophthalate containing 2 to 15 mol% of a monomer unit derived from isophthalic acid. Further, the present invention relates to a sheet and a film which have been subjected to a heat setting process.

The present invention further provides a foamed sheet having a density of 60 to 60.
700 kg / m ³ , the resin has a dissolution strength of more than 1 centinewton at 280 ° C., and has a dissolution viscosity of at least 1500 Pa. s
When heated at 120 ° C. for 10 minutes, the crystallinity becomes 3
Producing a uniaxially and biaxially stretched foamed sheet and film, comprising a step in which uniaxial or biaxial stretching is performed on a polyester resin foamed sheet having a crystallization ratio capable of reaching a value of 0 to 35%. The stretching is performed at a stretching ratio of 1.1: 1 to 5: 1. Also, the present invention relates to a method characterized in that the biaxial stretching is performed simultaneously or continuously in the machine direction and a direction perpendicular thereto, and the uniaxial stretching is performed in the machine direction or a direction perpendicular thereto. The invention further relates to articles consisting of uniaxially and biaxially oriented foamed sheets or films.

[0010]

DETAILED DESCRIPTION OF THE INVENTION The melt strength of available resins is at least 1 centinewton at 280.degree. C., and the melt viscosity is at least 280.degree.
00Pa. s. The dissolution strength is 10 to 150 centinewton or more, and the dissolution viscosity is 2000 to 20,000.
Pa. What is s is convenient for use. The melt strength of the resin making the foamed sheet or film was lower than the value of the resin used to make the sheet and film. Intrinsic viscosity is generally 0.8 to 1.5 dl / g
Between. The rheological properties specified above relate to the resin before the extrusion foaming treatment, but can also be obtained during said treatment.

The aromatic polyester resin used to obtain the resin having the above-specified rheological properties is prepared by mixing an aromatic dicarboxylic acid with 2-12
It is produced by polycondensation with a diol having two carbon atoms or by transesterification of a lower alkyl ester of dicarboxylic acid with a diol having 2 to 12 carbon atoms followed by polycondensation of a diol ester. Preferred aromatic acids include terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid.

The preferred resin is polyethylene terephthalate in which one or more 20 to 25, preferably 1 to 25 monomer units derived from terephthalic acid are replaced by a unit derived from isophthalic acid and / or naphthalenedicarboxylic acid, and a copolymer thereof. Polymers. The polyester resin having the above-specified rheological properties is obtained by adding an aromatic tetracarboxylic acid, particularly pyromellitic dianhydride to a polyester resin having an intrinsic viscosity of about 0.7 dl / g or less, in an amount of 0.05 to 2% by weight. The additions are obtained by solid polycondensation (SSP) under temperature conditions and durations that increase the melt strength and melt viscosity of the resin to selected values. The intrinsic viscosity of the resin after SSP is generally increased to a value of 0.8 dl / g or more.
The above-mentioned solid polycondensation is performed by a well-known method. A particularly preferred method is described in U.S. Pat. No. 524,3000, which is incorporated by reference. Preferred methods for obtaining the melt strength and melt viscosity values of the present invention are described in U.S. Pat. Nos. 5,288,764 and 5,229,432, which are incorporated by reference.

The polyester resin may be used by mixing another thermoplastic polymer, particularly a polyamide resin, in an amount of about 2 to 50% by weight. The method of producing this type of mixture or alloy is described in WO 94/09069, which is taken as a reference.
No. Particularly preferred polyamides for obtaining improved gas barrier properties (oxygen and carbon dioxide) include poly-m-xylilene adipamide. The polyamide is mixed during dissolution with 0.05 to 2% by weight of the polyester resin of a dianhydride of an aromatic tetracarboxylic acid, especially pyromellitic dianhydride, and a polyester resin previously mixed during the dissolution. You.

Other polymers which may be used include those obtained from aliphatic dicarboxylic acids and from diols, or from aliphatic hydroxides-acids or the corresponding lactones or lactides. A polyester resin is exemplified. A typical resin is poly-ε-propiolactone. These resins are used up to 40% by weight and impart biodegradable properties to the added resin.

In another aspect of the present invention, the addition of 0.5 to 10% by weight of an aliphatic or aromatic polyamide having a high or low molecular weight to a polyester resin allows the unreacted unreacted portions present in the stretched foamed sheet and film to be added. It has been discovered that the amount of pyromellitic dianhydride and the amount of acetaldehyde are significantly reduced.

The bulk density of the foamed sheets suitable for uniaxial and biaxial stretching is about 50~700kg / ^{m 3.} The thickness is usually 0.5 to 5 mm. To make a thin biaxially stretched foam film with a thickness reduced to about 30 microns, the thickness of the starting foam sheet is 0.6-2 mm. When a biaxially stretched sheet is obtained, a thicker sheet (2 to 5
mm). In the case of biaxial stretching, the bulk density after stretching increases significantly (as much as 4 times in the case of 4: 1 stretching). However, when a hydrocarbon is used as a foaming agent, the residual hydrocarbon contained in the cells expands when the sheet or film is heated to a temperature suitable for stretching. For this reason, it is also possible to obtain a biaxially stretched sheet or film having a lower density than before stretching.

In the case of uniaxial stretching, the density generally decreases (this is due to the use of different tools for biaxial and uniaxial stretching). In either case, the stretching is performed so that the density after stretching is preferably less than 500 kg / m ³ . The average cell size of the starting foam material varies between 0.01 and 1 mm depending on the conditions used for the extrusion foaming process, such as the type and amount of nucleating agent and blowing agent. Typical values are 0.2-0.4 mm. The average size of the cells of the sheet and film after biaxial stretching is larger than before stretching. In the case of uniaxial stretching, the cells stretch.

The biaxial stretching is performed using a conventional method at a temperature higher than the Tg of the polyester resin and lower than the melting point. Suitable temperatures are between 80 and 120C. The residence time during stretching is in the range of a few seconds to 40 seconds or more. The crystallinity of the sheet and film before stretching is sufficiently low (preferably less than 10%) so that stretching can be easily performed.

The biaxial stretching ratio in both directions is usually 1.5: 1 to 1.
The ratio is 5: 1, preferably up to 3: 1, and the stretching in two directions can be performed simultaneously or continuously. Uniaxial stretching can be performed in the machine direction or at right angles thereto. The stretching ratio is usually from 1.1: 1 to 4: 1. Stretching is
It is usually carried out on a series of calenders which are heated to 95-110 ° C. and rotate at different speeds.

In many cases, biaxially and uniaxially stretched materials are applied to the material at a temperature of, for example, 160 to 220 ° C. for several seconds (typically
~ 120 seconds) It is advantageous to apply a heat stabilization treatment. By this treatment, the dimensional stability of the material is increased, and the mechanical properties can be improved. The heat-set material is
It has relatively low heat shrinkage values compared to untreated materials (eg, less than 5% heat shrink at 180 ° C. for several minutes).

The crystallinity after stretching is higher than the crystallinity before stretching. In the case of stretched sheets and films that have been heat set, the value may be 30% or more. Thus, uniaxially and biaxially oriented foamed sheets and films have significantly improved mechanical properties compared to before stretching. The modulus and impact resistance are particularly high. For example, 4
In the case of a biaxially stretched film having a thickness of 0 micron, the coefficient reaches 2 GPa or more, and the ultimate tensile strength is 50-60M.
Pa and the breaking extension is 50%. The opacity of the stretched material is high, typically 40-80% for biaxially stretched films
It is. Gloss properties are significantly improved compared to unstretched foamed materials. Translucent sheets, especially those that have been biaxially stretched, are particularly suitable for use in holographic printing and the like because they exhibit a shiny reflection over the entire sheet.

The uniaxially and biaxially stretched sheets or films of the present invention are characterized by high levels of heat shrinkage.
For example, a biaxially stretched film having a thickness of 0.04 mm and a stretch ratio of 3: 1 is 20 to 30% when heated at 180 ° C. for several minutes.
Shows the contraction rate of This property is used in many practical applications, particularly for labeling polyester resin bottles that are applied to the bottle by shrinkage when the bottle is heated. Uniaxially and biaxially stretched sheets and films are used especially in the textile field due to their flexibility, breathability and high water vapor permeability. Also, its printability makes it particularly suitable for paper or cardboard replacement demand.

The uniaxially and biaxially stretched sheets and films may further comprise a multi-layered material in which one or both sides of the stretched sheet or film are adjacent to a layer of glass fiber reinforced polyester resin or low melting polyester resin or other material. It can also be included. The low melting polyester is usually copolyethylene terephthalate / isophthalate containing more than 7 mol% of isophthalic acid units. The multilayer material is a method of stretching the obtained multilayer material after co-extruding the resin forming the adjacent layer with the resin to be foamed from a set of extruders, or one or more other materials on a foamed sheet or film. Manufactured either by gluing or adhering to a sheet or film. Finally, biaxially stretched foam films and sheets have high opacity and high mechanical properties, making them particularly suitable for information technology and photographic applications. Other applications are not shown here, but will be apparent to those skilled in the art. The following examples are not intended to limit the scope of the present invention, but are described by way of illustration.

[0024]

EXAMPLES Measurement Method Intrinsic viscosity is measured using a 60/40 weight solution of phenol and tetrachloroethane at 25 ° C. according to ASTM D4603-86. Rheological measurements are performed at 280 ° C. using a Goettfert rheometer according to the ASTM D3835 standard. Melt strength measurements are determined by measuring in cN (centinewton) the force required to stretch the material extruded from the capillary of a Geotfert Rheograph 2002 rheometer. For the measurement, a Rheotens unit is added at the outlet of the capillary of the Geotofeld Rheograph 2002 rheometer.

Extrusion conditions are as follows. Piston Speed: 0.2 mm / sec die diameter: 2 mm capillary length: 30mm test temperature: 280 ° C. The measurements were performed by setting an acceleration to 2.4 cm / sec ^2.
Each measurement was repeated and the average of the two measurements was taken.

The crystallization ratio is determined by polyethylene terephthalate.
Percentage of crystallization rate
And the crystallization phase is correlated with the transformer configuration
Transformer arrangement and gauze correlated with
Determined by horizontal ATR (total reflection absorption) based on the ratio between
Is determined. ATR equipment is Perkin model 2000FT-
Attached to IR, measurement is 8cm ^-1Is performed by the analysis of
Sixteen scans were performed for clear measurements. Instrument cap
The crystallization is performed by the conventional density-column method.
PET sample whose amount of conversion was 7-65%
Was performed using The correlation coefficient was greater than 0.98. 1
410cm^-1The absorbance at was used as a reference band.

Example 1 Contains 2% of isophthalic acid (IPA) and has a dissolution strength of 28
150 centinewton at 0 ° C. and a melt viscosity of 30
1800 PA. At 0 ° C. and 10 rad / sec. S
The intrinsic viscosity is 1.24 dl / g, and the crystallization peak on the DSC curve (cooling rate 5 EC / min) in the dissolved state is 191E.
C, Delta H is 34 J / g;
90 kg / h of a polyethylene terephthalate copolymer obtained by regrading in the presence of 0.4% PMDA at is continuously fed to a twin screw extruder having a screw diameter of 90 mm. A static mixer was provided downstream of the screw to improve homogenization of the various components of the mixture. The temperature of the extruder was 280 ° C in the melting zone, 280 ° C in the compression zone, and 270 ° C in the mixing zone.
° C, and 265 ° C at the extrusion tip. The screw of the extruder turns at 18 rpm.

[0028] 3.6% by weight of nitrogen gas (blowing agent) is added to the resin in the area after the polymer dissolution area of the extruder, mixed thoroughly with the polymeric matrix and then cooled. The mixed and cooled resin / nitrogen composite is extruded through a 60 mm diameter annular tip and a 0.29 mm extrusion outlet. Downstream of the tip of the extrusion, a diameter of 200 mm and a length of 750
A cooling sizing mandrel cooled with water at 20 ° C in mm is installed. After leaving the mold, the foam material is placed on a mandrel, cut, pulled and then wound around a roll at a speed of 5 meters per minute by a winder for bobbin production.

The sheet has the following features. Density: 0.400 g / cm³  Thickness: 0.7 mm Average cell diameter: 230 microns Crystallinity: 8%
Axial stretching was performed. Table 1 shows the sheets before and after stretching.
Show some of the characteristics. The opacity of the sheet is 70% after stretching
Met. Before stretching, it was 92%. Gloss after stretching is 2
It was 32% at 0 ° C and 109% at 60 ° C. Corresponding delay
The values before elongation were 7.5% and 28%.

Example 2 Example 1 except that the extruder tip was provided with a 0.35 mm outlet instead of 0.29 mm and that the foam was collected on a roll at a rate of 3.9 meters per minute. And the same processing was repeated. Biaxial stretching at 110 ° C., stretching ratio 3:
Performed 1 and 4: 1. Table 1 shows some of the properties of the sheet before and after stretching.

Example 3 The same amount of n-pentane as 1.8% by weight was used as a blowing agent.
Except that, the same processing as in Example 2 was repeated.
The resulting sheet has the following properties. Density: 0.148 g / cm³  Thickness: 1.4 mm Average cell diameter: 300 microns Crystallinity: 8%

Example 4 The same amount of carbon dioxide as 2.4% by weight was used as a blowing agent.
Except for this, the same processing as in Example 1 was repeated. Profit
The resulting sheet has the following properties: Density: 0.280 g / cm³  Thickness: 1 mm Average cell diameter: 220 microns Crystallinity: 8% Sheet after biaxial stretching at 100 ° C. and stretching ratio of 3: 1
Are the same as those of the sheet after stretching in Example 1.
You.

Example 5 IPA was contained at 7.5% and the cooling rate was 5 ° C./min.
Endothermic peak in the DSC curve of
Copolyethylene terephthale with a tropy of 24 j / g
The same processing as in Example 1 was repeated, except that
I returned. The resulting sheet has the following properties. Density: 0.395 g / cm³  Thickness: 1.2 mm Average cell diameter: 208 microns Crystallinity: 8% The sheet is biaxially stretched at 100 ° C, and the stretching ratio is bidirectional.
Both were 3: 1. The thickness of the sheet after stretching is 0.04
mm, and the density is 910 kg / m³And opacity
Was 75%.

Example 6 The stretched sheet of Example 2 (stretch ratio: 3: 1) was subjected to a heat stabilization treatment at 210 ° C. for 10 seconds. The elastic modulus is 1.2 GP
a, the ultimate tensile strength is 29 Mpa and the breaking elongation is 3
3%.

[Table 1]

Example 7 2.5% by weight of polym-xylylene adipamide (poly MXD-66 manufactured by Mitsubishi Gas Chemical Company) was added to the copolyethylene terephthalate and PMDA used in Example 1.
Example 1 was repeated except that 121) was added. The sheet having a thickness of 0.04 mm stretched biaxially at a stretch ratio of 3: 1 in both directions has an oxygen permeability of 80 ml.
/ M ² / day, and the transmittance of the sheet containing no poly-MXD-6 was 96 (before stretching, the sheet was poly-MXD-6).
Was 13 and the transmittance of the sheet containing no polyamide was 15). The content of free (unreacted) PMDA was 2 ppm and the content of acetaldehyde was 2-3 ppm.

Example 8 The melt strength and melt viscosity characteristics described in Example 1 were
Endothermic peak in DSC curve from dissolution at rejection rate of 5EC / min
Temperature is 201 ° C and delta entropy is 38j / g
Using a PET homopolymer, the same amount of nitrogen as 1.3 wt%
Except for using a foam (foaming agent),
Repeated. The resulting sheet has the following properties. Density: 0.450 g / cm³  Thickness: 1.1 mm Average cell diameter: 300 microns Crystallinity: 8% The sheet is heated to 95EC and rotates at different speeds.
Stretched by a series of calendar units.

The results of a vertical impact test using a Franctovis Ceast impactor (collision test apparatus) are shown in Table 2 with respect to the stretch ratio (stretch in the machine direction) used.

[Table 2]

For comparison, a thickness of 0.4 obtained from a commercial fruit container based on polyethylene-treated cardboard was used.
For the 5 mm test piece, the peak energy value (the energy at which fracture begins to appear) was 0.16 J, and the total energy was 0.5 J, corresponding to the perforation energy of the test piece after impact.

[0039]

The uniaxially and biaxially oriented polyester resin foam sheets of the present invention have relatively low apparent densities and high translucency associated with high mechanical properties, especially high modulus and high impact resistance and spark reflectivity. Or opacity. Therefore, it is suitable for use in labeling holographically printed polyester resin bottles, in the field of textiles, and in demand for replacement of paper or cardboard.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) B29K 67:00 B29L 7:00 (72) Inventor Sandro Coblo Italy 86077 Poggigli (Province of Isania) Largo Parazzo Del Prito 3 (72) Inventor Tonino Severini Italy 00034 Corfero (Province of Rome) Via del Solve 31

Claims (15)

[Claims] 1. A solution having a melt strength of more than 1 centinewton at 280 ° C. and a melt viscosity at 280 ° C. of at least 1500 Pa. s and 120 ° C
Uniaxially or biaxially stretched foamed sheets and films made from an aromatic polyester resin having a degree of crystallinity that can reach a value of 30 to 35% upon heating at 10 minutes. 2. A bulk density value of 100 to 1000 kg / m.
^3. The uniaxially and biaxially stretched sheet and film according to claim 1, wherein the thickness is in the range of ³ . 3. The sheet and film according to claim 1, wherein the thickness is 0.03 to 1 mm. 4. The resin has a crystallization ratio of 10 ° C. at 120 ° C.
The sheet and film according to claim 1, wherein the degree of crystallization is such that the degree of crystallization is 5 to 20% when heated for a minute. 5. The sheet and film according to claim 1, wherein 0.5 to 10% by weight of polyamide is mixed with the polyester resin. 6. The sheet and film according to claim 5, wherein the polyamide is poly-m-xylylene adipamide. 7. The sheet and film according to claim 1, wherein the polyester resin is polyethylene terephthalate or copolyethylene terephthalate-isophthalate containing 2 to 15 mol% of an isophthalic acid unit. 8. A multilayer material comprising the sheet or film according to claim 1 and one or more layers of another material adhered to one or both sides of the foamed sheet or film. 9. The method of claim 1, wherein at least one layer adhered to the foamed sheet or film is copolyethylene terephthalate-isophthalate containing 2 to 15 mol% of a monomer unit derived from isophthalic acid. Item 8. The multilayer material according to Item 8. 10. The sheet and film according to claim 1, which have been subjected to a heat setting treatment. 11. The foamed sheet has a density of 60 to 700 kg.
/ M ³ , and the resin has a crystallinity that can reach a value of 30 to 35% by heating at 120 ° C. for 10 minutes, and has a dissolution strength of more than 1 centinewton at 280 ° C. And at least 1500 Pa.s so that the melt viscosity is 280 ° C. and the shift speed is zero. The method for producing a sheet and a film according to any one of claims 1 to 10, further comprising a step in which uniaxial or biaxial stretching is performed on the polyester resin foam sheet that is s. 12. The method according to claim 11, wherein the stretching is performed at a stretching ratio of 1.1: 1 to 5: 1. 13. The method according to claim 12, wherein the biaxial stretching in the machine direction and in a direction perpendicular thereto is performed simultaneously or continuously. 14. The method according to claim 13, wherein the uniaxial stretching is performed in a machine direction or a direction perpendicular thereto. 15. A product comprising the sheet or film according to claim 1.